marlou pan,
It's possibly a Marasmiellus pseudostem and root rot.
Good drainage and mixed plantings of many different banana clones; and the inclusion of tree crops, might make a difference. Strongly advise your client to abandon monoculture.
It is killing the banana "industry" in the Philippines.
Devise a business model for a mixed output farm, with possible processing on-farm. Value-added must accrue to the farmer.
Banana breeders cannot produce (vertically) resistant varieties to pathogens evolved under monoculture.
In the absence of any definitive data - that's the best I can suggest.
shannon
shannon.di.corse@gmail.com